Section 1, Table 4 - Hardware & technology strategy & planning

Edit 0 6 …
Week 4
Slide 4
Week 4 Keywords
Technology Hype Circle
Information Technology Strategy: Three Misconceptions

3 misconceptions:
  • The IT strategy should solely derived from a thorough review of organizational strategies and plans
  • The IT strategy should be dominated by a focus on defining needed application systems
  • The IT strategy is better if it is developed by using a rigorous methodology

3 Ways to allocate space on a hard drive
  • contiguous
  • linked
  • indexed

Contiguous Model
  • requires each file to occupy a set of contiguous blocks on the disk
  • simple- file designations only need to include the starting location (#) and how many blocks are required
  • Dynamic storage allocation is difficult
  • the problem of external fragmentation
  • Allocation voes
  • files can't grow

Linked Model
  • solves problem of contiguous allocation
  • Each file is linked list of disk blocks- scattered anywhere on the disk
  • No external fragmentation- files can grow
  • file allocation tables uses

Indexed Model
  • solves external fragmentation and size declaration issues with contiguous allocation
  • each file contains index block
  • However suffers from wasted space

FAT (File Allocation Table)
  • FAT has an entry for only disk block
  • FAT entries rather than blocks themselves are linked
  • Disk sectors are grouped into clusters

Fragmentation
  • as computer files are added/deleted, parts of files tend to become scattered all over the disk
  • "Holes" are left in the file system that are too small to fill
  • Slows performance of read/write/access
  • Defrag must be run to rearrange

Types of Fragmentation
  • Internal- allocate storage without using it
  • External- free space divided into small pieces over time
  • Data- data broken in memory into many small pieces due to external fragmentation